linux-kernel - Re: [PATCH 01/14] resource limits: foundation for resource highwater tracking

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Date:	Fri, 15 Jul 2016 14:49:40 +0200
From:	Nicolas Dichtel <nicolas.dichtel@...nd.com>
To:	Topi Miettinen <toiwoton@...il.com>, linux-kernel@...r.kernel.org
Cc:	Jonathan Corbet <corbet@....net>, Ingo Molnar <mingo@...hat.com>,
	Peter Zijlstra <peterz@...radead.org>,
	Balbir Singh <bsingharora@...il.com>,
	"David S. Miller" <davem@...emloft.net>,
	Markus Elfring <elfring@...rs.sourceforge.net>,
	Thomas Gleixner <tglx@...utronix.de>,
	Rik van Riel <riel@...hat.com>,
	"open list:DOCUMENTATION" <linux-doc@...r.kernel.org>
Subject: Re: [PATCH 01/14] resource limits: foundation for resource highwater
 tracking

Le 15/07/2016 12:35, Topi Miettinen a écrit :
> There are many basic ways to control processes, including capabilities,
> cgroups and resource limits. However, there are far fewer ways to find out
> useful values for the limits, except blind trial and error.
> 
> Prepare a foundation for resource highwater tracking.
> 
> The collected highwater marks for the resources can be seen using
> taskstats netlink interface.
> 
> This depends on CONFIG_TASK_XACCT.
> 
> Signed-off-by: Topi Miettinen <toiwoton@...il.com>
> ---
[snip]
> @@ -63,6 +65,8 @@ int print_task_context_switch_counts;
>  /* Maximum number of cpus expected to be specified in a cpumask */
>  #define MAX_CPUS	32
>  
> +#define TASKSTATS_VERSION_WITH_RESOURCE	9
> +
>  struct msgtemplate {
>  	struct nlmsghdr n;
>  	struct genlmsghdr g;
[snip]
> @@ -252,6 +276,22 @@ static void print_ioacct(struct taskstats *t)
>  		(unsigned long long)t->cancelled_write_bytes);
>  }
>  
> +static void print_racct(const struct taskstats *t)
> +{
> +	int i;
> +
> +	if (t->version < TASKSTATS_VERSION_WITH_RESOURCE) {
> +		printf("kernel too old (%d < %d)\n", t->version,
> +		       TASKSTATS_VERSION_WITH_RESOURCE);
> +		return;
> +	}

[snip]
> diff --git a/include/uapi/linux/taskstats.h b/include/uapi/linux/taskstats.h
> index 2466e55..8c65194 100644
> --- a/include/uapi/linux/taskstats.h
> +++ b/include/uapi/linux/taskstats.h
> @@ -33,7 +33,7 @@
>   */
>  
>  
> -#define TASKSTATS_VERSION	8
> +#define TASKSTATS_VERSION	9
>  #define TS_COMM_LEN		32	/* should be >= TASK_COMM_LEN
>  					 * in linux/sched.h */
>  
> @@ -163,6 +163,14 @@ struct taskstats {
>  	/* Delay waiting for memory reclaim */
>  	__u64	freepages_count;
>  	__u64	freepages_delay_total;
> +	/* Per-task storage I/O accounting ends */
> +
> +#define TASKSTATS_HAS_LIMIT_ACCOUNTING
> +	/* Per-task resource accounting starts */
> +	__u64   resource_hiwater[RLIM_NLIMITS]; /* high-watermark of
> +						     RLIMIT
> +						     resources */
> +	/* Per-task resource accounting ends */
>  };
Why playing with version number? It complexifies the (userland) code and
existing applications break when the kernel is updated.
Goal of netlink is to be easily extensible. By adding a new attribute, existing
userspace tools won't break.


Regards,
Nicolas